Floating oil storage installation

ABSTRACT

Floating oil storage tank has a roof and an open bottom. Upper part of tank beneath the roof may serve as a pontoon for floating the tank when no oil is stored in it. The pontoon may house offices, equipment room, operations room, and lodgings. The tank may be secured to fixed anchors on the sea bottom or to a rotatable anchor about which the tank rotates depending upon the direction of the wind, waves, and tide. Oil may be supplied to the tank from a submarine pipe line through the rotatable anchor. Wave protectors may be carried externally of the tank, and may be either fixed or rotatable with respect to the tank. The top wall of the upstream wave protector, with respect to the direction of wave movement, may be sloped to reduce up and down movement of the tank. The tank may have internal sludge collecting and depositing means. A plurality of tanks may be bonded together and a tanker temporarily bonded to the tanks during discharge of oil into the tanker.

United States Patent Hirata Dec. 18, 1973 FLOATING OIL STORAGE INSTALLATION Assistant Examiner-Stuart M. Goldstein [76] Inventor: Hiroshi Hirata, 15-30, Z-chome Ammey Alan Levme et Sanno, Ota-ku, Tokyo, Japan [22] Filed: Jan. 6, 1972 ABSTRACT [21] APPL 217,705 Floating oil storage tank has a roof and an open bottom. Upper part of tank beneath the roof may serve as a pontoon for floating the tank when no oil is stored in [30] Forelgn Apphcmlo" Pnonty Data it. The pontoon may house offices, equipment room,

Jan. 8, 1971 Japan 46/150 operations room, and lodgings. The tank may be secured to fixed anchors on the sea bottom or to a rotat- [52] US. Cl. 1l4/0.5 T able anchor about which the tank rotates depending [51] Int. Cl B63!) 35/00 upon the direction of the wind, waves and tide. Oil [58] Field of Search 114/.5 T; 9/8 P; may be supplied to the tank from a submarine pipe 1/ 65 line through the rotatable anchor. Wave protectors may be carried externally of the tank, and may be ei- [56] References Cited ther fixed or rotatable with respect to the tank. The UNITED STATES PATENTS top wall of the upstream wave protector, with respect 3,327,667 6/1967 Manning 114/.5 T to the direction of wave movement may be sloped to 3,5995% 8/197 Rego v reduce up and down movement of the tank. The tank 3.472,032 10/1969 Howard 9/8 PX y have internal Sludge Collecting and depositing means. A plurality of tanks may be bonded together FOREIGN PATENTS OR APPLICATIONS and a tanker temporarily bonded to the tanks during 113L036 discharge of oil into the tanker.

9/1960 France 114/.5 T

Primary Examiner-Trygve M. Blix 15 Claims, 14 Drawing Figures PMENIEUUEC 18 1925 3,779.1 93

SHKEI 10? 5 PATENIEU DEC 18 1925 SHEET 2 BF 5 PATENIEDDEC 18 1915 saw u er s 1 FLOATING OIL STORAGE INSTALLATION This invention relates to a floating tank in which crude oil or petroleum oil products are stored at sea or in a lake. As the quantity of oil stored in the tank in creases, sea water flows out from the bottom of the tank, and as the quantity of oil decreases, sea water flows in through the bottom to replace the oil.

The floating tank of the present invention is safe, economic, and easy to operate and maintain. In addition, the tank prevents pollution of the surrounding sea.

The tank of this invention controls the floating force produced by the difference in specific gravities of oil and sea water. In addition, room is provided at the upper part of the tank to serve as a pontoon, the pontoon being separated from the oil storage part of the tank and insuring that the top of the tank always floats on the sea surface. In the event that a leak occurs in the roof of the tank, which is also the roof of the pontoon, the tank can be sunk into the sea without trouble, Furthermore, the interior of the pontoon can be used to house an office, operations room, equipment room, and lodgings, and the roof of the tank may be equipped with a pump and motor for withdrawing oil from the tank.

The floating tank of this invention may be furnished with wave protectors. A floating tank receives a positive wave force on the upstream side with respect to the direction of wave movement, and a negative force acts on the downstream side of the tank. The wave force acting on the floating tank is the total of these values, and can become very large. Furthermore, the force may act unevenly on the tank, and therefore conventionally a floating tank must be a very strong and large structure. Furthermore, such a tank requires strong moorings to prevent its being carried away by the waves.

To prevent the wave force acting directly on the shell of the floating tank of the present invention, the tank is equipped with wave protectors. As a result, the tank can be made more economically than conventional tanks, and a less substantial mooring is required.

The wave protectors may serve simultaneously as pontoons, and can be used as equipment rooms. Furthermore, the upper surface of the wave protector on the upstream side of the tank may be sloped so as to be stabile when tilted by waves. Furthermore, the tank may be moored at a single anchor connected to the wave protector by a chain. Thus, the tank is able to move around the anchor depending on the direction of the wind and waves, the anchor serving as the center of this movement and the length of the chain defining the radius of this movement. The oil pipe line may be furnished with a suitable joint at the anchor so that the tank can receive oil regardless of its position with respect to the anchor.

According to the invention, means are provided to prevent pollution of the sea with matter floating in the oil. A perforated cylindrical tube or net is suspended concentrically at the center of the tank, and this tube or net collects the matter floating in the oil and deposits it rapidly on a deposit plate within the tank. When the oil is discharged from the tank, the deposit is blended with the oil and discharged from the tank with the oil.

The invention also provides for bonding together two or more tanks moored at a single anchor. A tanker may then be temporarily moored at the floating tanks, and

oil may be discharged from the tanks into the tanker or vice versa. As a result of this arrangement, it is not necessary to provide each floating tank with a separate pipe line and mooring. Instead, a single pipe line and mooring can serve several tanks, and hence the cost of construction and operation is reduced. Hoses intercon' nect the bonded tanks to permit each to receive oil and have oil discharged from it.

The invention will be described in more detail with reference to the accompanying drawings, in which:

FIG. 1 is a vertical cross-sectional view of a floating tank according to the present invention, the tank having no oil stored in it and its top part floating on the sea surface and being restrained by two anchors;

FIG. 2 is a view similar to FIG. 1, but with a maxi mum quantity of oil stored in the tank;

FIG. 3 is a diagram of the pressures in FIG. 2, showing the relation of the theoretical height of stored oil due to the difference in specific gravities of oil and sea water, and the decrease of the stored oil surface due to the weight of the floating tank;

FIG. 4 is a vertical cross-sectional view of a floating tank similar to the one shown in FIG. 1, the tank being equipped with fixed wave protectors and being moored to a single rotatable anchor used both for mooring and for receiving oil;

FIG. 5 is a plan view of FIG. 4;

FIG. 6 is a vertical cross-sectional view of a floating tank having wave protectors which are also used as pontoons, the tank being moored to an anchor similar to the one shown in FIG. 4;

FIG. 7 is a plan view of FIG. 6;

FIG. 8 is a vertical cross-sectional view of a floating tank similar to the one shown in FIG. 1, but provided with rotatable wave protectors and equipped internally with means for collecting sludge floating in the oil;

FIG. 9 is a plan view of FIG. 8;

FIG. 10 is a fragmentary vertical cross-sectional view of a connector by means of which the rotatable wave protector is mounted on the tank;

FIG. 11 is a vertical cross-sectional view of two tanks, similar to the one shown in FIG. 6, bonded together, oil being discharged from the tanks into a tanker;

FIG. 12 is a plan view of FIG. 11; and

FIGS. 13a and 13b are schematic plan views showing alternative shapes for the wave protectors.

In the following description, the same reference numerals and symbols are used to identify corresponding parts in each figure.

FIG. 1 shows a floating tank 3 in a sea having a surface 1 and a bottom 2, the depth of the sea being identifled as H. The floating tank has a diameter D and a roof 6, but is open at the bottom. The upper part of the tank forms a pontoon 4 defined by the roof 6 and a bottom plate 5. A platform 16 is mounted on the roof 6. An equipment room, operations room and lodgings 52 are provided in the pontoon 4. A hollow shaft 15 is provided at the center of the pontoon 4, and a pump 10 operated by a motor 11 is located within the shaft.

Oil to be stored in the tank 3 flows into the tank through a submarine pipe line 12, a hose l3, and an opening 14 immediately below bottom plate 5. Oil could also be introduced into the tank through suitable openings in the roof 6 or shell of the tank, but such openings are not shown.

At its lower edge, tank 3 is provided with rings 7 each of which is connected to an anchor 9 by a chain 8. By

thus anchoring the tank to the sea bottom 2, the tank is prevented from being carried away by billows, winds, and tides.

The bottom plate 5 is' positioned to give the pontoon 4 a selected draft a considering the total weight of the floating tank and attached equipment supported by the pontoon. The draft a of the pontoon is such that roof 6 is always above the sea surface 1 even when no oil is stored in the tank.

FIG. 2 shows tank 3 holding the maximum quantity of oil 19 which can be stored in the tank.

FIG. 3 indicates the water pressure, Pw, which is equal to the depth h of the stored oil, i.e., the depth from the sea surface 1 to the bottom surface 24 of the stored oil 19. The oil pressure Po at the bottom surface 24 of the oil is also indicated in FIG. 3, as is the height ha of the free oil surface under atmospheric pressure and the height d of the free oil surface above the sea surface 1. If rw represents the specific gravity of water, and r represents the specific gravity of the oil, the following relationships can be established:

d ho h and Pw=h rw P0 h0.r0 Pw P0 Then, h.rw h0.r0; ho h rw/ro, From the formula 1 d=h rw/ro h If the total weight of the floating tank and attached equipment is W, the free oil surface drops by an amount c as shown in FIG. 3. c is calculated from the following formula:

Bottom plate of the pontoon 4 has risen a height b from sea surface 1. b is calculated from the following formula,

When the tank is empty, the bottom plate 5 of the pontoon is kept at draft a, as shown in FIG. 1, and is situated under sea surface ll.

Draft a is calculated from the following formula,

When draft a has been calculated from the above formula, and height b has been measured, the increase or decrease in the amount of stored oil can be calculated from the amount the floating tank has risen or fallen.

FIGS. 4 and 5 illustrate a floating tank 3 having wave protectors l7 and 17 fixed to it. Wave protector 17 is on the upstream side of the tank with respect to the direction of wave'movement, which is indicated by the arrows F. The wave protectors 117 and 17' are shaped to dampen the wave force as compared to the situation when the wave force acts directly upon the cylindrical surface of the floating tank.

Ordinarily, in the absence of wave protectors, the wave force acts violently on the shell of the floating tank 3 with an uneven external force, and as a result this structure must be made large and strong. However, according to the present invention, the wave protector 17 catches the wave force, and this force is then transmitted to the rotatable anchor 9 along chains 8 and 8' and hence the force is not transmitted to the wall of the floating tank. Thus, providing wave protectors 17 and 17' on the upstream and downstream sides, respectively, of the floating tank 3 prevents the effect of billows from acting upon the external wall of the tank. As a result, the tank shell is safe even though not reinforced, as is usually the case.

The amount of floatation provided by the wave protectors 17 and 17' can be adjusted by varying the amount of liquid 18 inside them. Furthermore, the upper part of each wave protector can be used to house an equipment room, operations room and lodgings.

So that tank 3 can receive oil from submarine pipe line 12, hose 13 is connected to the single rotatable anchor joint 9 to which the tank is moored. Anchor joint 9 is made integral with a rotatable joint 40 rotatable within a globular casing 41. Thus, oil is pipe line 12 flows through joint 40, 41, hose l3, and opening 14 into the tank.

The casing 41 of the rotatable joint is fixed to the sea bottom 2 by piles 42. If desired, instead of using rotatable joint 9 as described above, tank 3 can be attached to a mooring buoy of a conventional type which permits the tank to rotate about it but still can deliver oil to the tank.

FIGS. 6 and 7 show a floating tank 3, similar to the tank of FIG. 4, but without a pontoon 4. Instead, the wave protectors l7 and 17 of this tank provide all the buoyancy needed to float the tank. The oil 19 stored in the tank has a free oil surface 24' under atmospheric pressure. The floating force provided by the wave protectors can be adjusted by varying the amount of liquid 18 within the wave protectors.

The top wall of the upstream wave protector l7 slopes downwardly and outwardly to reduce the amount of up and down motion produced on the floating tank by waves. The height of sea waves can vary from a few meters to ten or more meters, and since the wave force travels in a horizontal direction, the tank is moved up and down.

As indicated in FIG. 6, if the wave force in a horizontal direction is identified as P, the angle of slope of the top wall 47 of wave protector 17 is 6, the component of the wave force perpendicular to top wall 47 is Pv, and the rectangular component of Pv is Pp, then Pv P cos0, and

Pp Pv sin0, and therefore,

Pp P cosO sinO Pp in the wave force P is the only downward force acting on the tank 3, and this force is reduced by using the sloping wall 47 so that the up and down motion of the tank is also reduced.

The arrangement is more effective in preventing up and down motion of the tank if wave protector 17 is equipped with plates 50. In addition, if desired, pontoons 51 may be provided inside or outside tank 3.

FIGS. 8 and 9 show a floating tank similar to that of FIG. 1, except that the tank is provided with wave protectors 17 and 17' secured to the tank by rotatable connectors 20, and the tank is provided with internal sludge-gathering equipment. This equipment includes perforated cylindrical tubes or nets 21 which gather material floating in the oil within the tank, and a deposit plate 22 suspended by members 22 upon which the sludge is deposited.

The upstream and downstream wave protectors l7 and 17', respectively, are interconnected by connecting members 48, and can rotate bodily around the external periphery of the tank, the center of this rotation being concentric with the center of the tank. The position to which the wave protectors are rotated depends upon the direction of the tide, waves, and wind.

The periphery of the deposit plate 22 is separated from the wall of tank 3 by a space 49, and the plate 22 is located at about the center of the tank. The hose through which oil enters the tank has, for convenience, not been shown in FIG. 8. However, the oil enters the tank immediately below bottom plate 5 and near the center of the tank. The oil flows out of the tank at a very slow velocity in the direction of the periphery of deposit plate 22. During this flow, sludge floating in the oil is gathered by the perforated tube or net 21 and is gathered in the deposit tank 23 at the center of deposit plate 22.

After the sludge has been deposited on the upper surface of deposit plate 22, the oil flows out through space 49 and into the portion of the tank beneath plate 22. Deposit 26 is mixed with sea water in the upper part of deposit tank 23 and deposit plate 22 and is discharged by a sea water pump (not shown). If desired, the deposit or sludge 26 could be circulated and delivered in a jet on deposit plate 22 by pump through a separate pipe system (not shown), or the sludge could be dissolved and floated by heating and discharged with the discharging oil. Any of the embodiments shown in FIGS. 1, 4, and 6 may be provided with the sludge gathering equipment described above.

FIG. 10 shows the rotatable connection in more detail. Wall of each wave protector carries a T- shaped shaft 29 provided with rollers 27. Rollers 27 are subjected to the horizontal wave force. Shaft 29 also carries rollers 28, which are subjected to the up and down wave force. The rollers 27 and 28 are arranged to cooperate with an annular guide or track formed by two L-shaped members 31 and 31' secured to the external wall of tank 3.

FIGS. 11 and 12 show two tanks 3, of the type illustrated in FIG. 6, bonded together and discharging oil through hoses into a tanker 34. The two floating tanks, identified as 32 and 33, have wave protectors 17 and 17', respectively, and the upstream wave protector 17 of tank 33 is connected to the downstream wave protector 17 of tank 32 by chains 39 and 39 and connecting pins 38 and 38.

Both floating tanks 32 and 33 are moored to a single rotatable anchor joint 9 by chains 8 and 8'. Oil enters tank 32 through hose 13, and flows through hose 36 from tank 32 into tank 33. In this way both tanks are filled with oil 19 and 19, respectively. Each tank is furnished with gunwale protectors 37 and has its own hose 35 for delivering oil to the tanker 34.

With the arrangement of the floating tanks 32 and 33, and the tanker 34, as described above, during discharge of oil from the tanks into the tanker, the tanks and tanker are able to rotate about the rotatable joint 9 depending on the direction F of the waves, wind, and tide.

It will be seen, therefore, that there is not need to install a submarine pipe line from the floating tanks to a sea berth for a tanker. This keeps construction cost low and makes operation very simple. The embodiment described above shows two tanks bonded together. However, it is also possible to bond more than two tanks together and to fill more than two tankers from these tanks simultaneously, all the tanks and tankers being connected to a single mooring.

It may be mentioned that the floating tank shown in FIG. 8 may also be bonded to other floating tanks and a tanker moored to these bonded tanks while oil is discharged into the tanker.

FIGS. 13a and 1312 are plan views of other types of wave protectors carried by floating tanks 3. FIG. 13a shows wave protectors 44 having external convex surfaces, and FIG. 13b shows wave protectors 45 having concave external surfaces.

The floating tanks of the present invention may be provided with oil surface indicators and water surface indicators (not shown) to indicate the location of bottom oil surface 24 and free oil surface 24' as a guide to the operating personnel of the tank.

What is claimed is:

l. A floating oil storage installation including a tank having a closed top, an open bottom, and a longitudinal axis substantially perpendicular to the top and bottom; means for introducing oil to be stored into the upper part of said tank; means for pumping oil out of said tank, sea water entering said tank through its open bottom when oil is pumped out of said tank and the sea water being pushed out of said tank through its open bottom when oil is introduced into said tank; pontoon means fixed to said tank for maintaining the tank in floating condition when no oil is stored in it; and at least one elongated wave protector carried by the exterior of said tank, said wave protector including walls converging outwardly from said tank, each of said walls terminating at its outer edge at a surface which is much narrower than the width of said wall, the longitudinal axis of the wave protector being substantially parallel to the longitudinal axis of the tank.

2. A floating oil storage installation as defined in claim 1 wherein said pontoon means is defined by a space within said tank directly beneath its closed top.

3. A floating oil storage installation as defined in claim 2 including means within said space defining accommodations for equipment and personnel.

4. A floating oil storage installation as defined in claim 1 including two such wave protectors arranged diametrically opposite to each other.

5. A floating oil storage installation as defined in claim 1 wherein said wave protector is fixed to said tank.

6. A floating oil storage installation as defined in claim 1 wherein said wave protector is rotatable with respect to, and about the periphery of said tank.

7. A floating oil storage installation as defined in claim 6 including an annular guide fixed around the periphery of said tank, and rollers carried by said wave protector movable along said guide.

.8. A floating oil storage installation as defined in claim 1 wherein said wave protector is hollow and defines said pontoon means.

9. A floating oil storage installation as defined in claim 1 including an anchor having a part fixed to the sea bottom and a part rotatable with respect to said fixed part, and means securing said tank to said rotatable part.

10. A floating oil storage installation as defined in claim 9 wherein said anchor forms part of said means for introducing oil into said tank, oil flowing through said fixed and movable parts toward said tank.

11. A floating oil storage installation as defined in claim 1 including means within said tank for collecting sludge carried by the oil.

12. A floating oil storage installation as defined in claim 11 wherein said sludge-collecting means includes a perforated tubular member in the upper central part of said tank, and a deposit plate beneath said member.

13. A floating oil storage installation as defined in claim 12 wherein the periphery of said deposit plate is spaced from the interior wall of said tank.

14. A floating oil storage installation as defined in claim 1 including a plurality of said tanks, means bonding said tanks together, and conduit means through which oil can flow from one of said tanks into another, whereby only said one tank need be furnished with means for introducing oil into it, the oil flowing through said conduit means to said other tank.

15. A floating oil storage installation including: a

tank having a closed top and an open bottom; means for introducing oil to be stored into the upper part of said tank; means for pumping oil out of said tank, sea water entering said tank through its open bottom when oil is pumped out of said tank and the sea water being pushed out of said tank through its open bottom when oil is introduced into said tank; pontoon means fixed to said tank for maintaining the tank in floating condition when no oil is stored in it; at least one wave protector connected by a coupling to the outside of the tank, said wave protector including walls converging outwardly from said tank, the coupling including an annular guide fixed around the periphery of said tank, and rollers carried by said wave protector movable along said guide, whereby said wave protector is rotatable about the periphery of said tank. 

1. A floating oil storage installation including a tank having a closed top, an open bottom, and a longitudinal axis substantially perpendicular to the top and bottom; means for introducing oil to be stored into the upper part of said tank; means for pumping oil out of said tank, sea water entering said tank through its open bottom when oil is pumped out of said tank and the sea water being pushed out of said tank through its open bottom when oil is introduced into said tank; pontoon means fixed to said tank for maintaining the tank in floating condition when no oil is stored in it; and at least one elongated wave protector carried by the exterior of saiD tank, said wave protector including walls converging outwardly from said tank, each of said walls terminating at its outer edge at a surface which is much narrower than the width of said wall, the longitudinal axis of the wave protector being substantially parallel to the longitudinal axis of the tank.
 2. A floating oil storage installation as defined in claim 1 wherein said pontoon means is defined by a space within said tank directly beneath its closed top.
 3. A floating oil storage installation as defined in claim 2 including means within said space defining accommodations for equipment and personnel.
 4. A floating oil storage installation as defined in claim 1 including two such wave protectors arranged diametrically opposite to each other.
 5. A floating oil storage installation as defined in claim 1 wherein said wave protector is fixed to said tank.
 6. A floating oil storage installation as defined in claim 1 wherein said wave protector is rotatable with respect to, and about the periphery of said tank.
 7. A floating oil storage installation as defined in claim 6 including an annular guide fixed around the periphery of said tank, and rollers carried by said wave protector movable along said guide.
 8. A floating oil storage installation as defined in claim 1 wherein said wave protector is hollow and defines said pontoon means.
 9. A floating oil storage installation as defined in claim 1 including an anchor having a part fixed to the sea bottom and a part rotatable with respect to said fixed part, and means securing said tank to said rotatable part.
 10. A floating oil storage installation as defined in claim 9 wherein said anchor forms part of said means for introducing oil into said tank, oil flowing through said fixed and movable parts toward said tank.
 11. A floating oil storage installation as defined in claim 1 including means within said tank for collecting sludge carried by the oil.
 12. A floating oil storage installation as defined in claim 11 wherein said sludge-collecting means includes a perforated tubular member in the upper central part of said tank, and a deposit plate beneath said member.
 13. A floating oil storage installation as defined in claim 12 wherein the periphery of said deposit plate is spaced from the interior wall of said tank.
 14. A floating oil storage installation as defined in claim 1 including a plurality of said tanks, means bonding said tanks together, and conduit means through which oil can flow from one of said tanks into another, whereby only said one tank need be furnished with means for introducing oil into it, the oil flowing through said conduit means to said other tank.
 15. A floating oil storage installation including: a tank having a closed top and an open bottom; means for introducing oil to be stored into the upper part of said tank; means for pumping oil out of said tank, sea water entering said tank through its open bottom when oil is pumped out of said tank and the sea water being pushed out of said tank through its open bottom when oil is introduced into said tank; pontoon means fixed to said tank for maintaining the tank in floating condition when no oil is stored in it; at least one wave protector connected by a coupling to the outside of the tank, said wave protector including walls converging outwardly from said tank, the coupling including an annular guide fixed around the periphery of said tank, and rollers carried by said wave protector movable along said guide, whereby said wave protector is rotatable about the periphery of said tank. 